Clot-Blocking Drug Combats Severe Heart Attacks

Plavix keeps arteries open, improves survival rates, studies find

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WEDNESDAY, March 9, 2005 (HealthDay News) -- Adding the clot-preventing drug Plavix to the treatment of people with severe heart attacks helps reopen their clogged arteries and saves lives.

That's the finding of two studies presented Wednesday at the American College of Cardiology's annual scientific sessions in Orlando, Fla.

Plavix reduces clotting by preventing the blood cells called platelets from clumping together. It's now used to prevent artery blockage in people at high risk of heart attacks and those who undergo the artery-opening procedure called angioplasty.

A U.S. study of nearly 3,500 people treated in the first hours after a heart attack showed that those who got Plavix in addition to a clot-dissolving drug and aspirin -- the current standard treatment -- were 36 percent less likely to die or to have another heart attack, reported Dr. Marc S. Sabatine, an associate physician at Brigham and Women's Hospital in Boston, and a leader of the study.

"This treatment applies to patients coming in with the most severe form of heart attack, where the artery is completely blocked," Sabatine said. "There are about a million heart attacks in the United Stats every year, and about a third of them are the severe kind, where the artery needs to be reopened immediately."

The study will be published in the March 24 issue of the New England Journal of Medicine.

One weakness of the trial is that it was not large enough to show that Plavix treatment improves long-term survival, said Dr. Richard A. Lange, chief of clinical cardiology at the Johns Hopkins School of Medicine and co-author of an accompanying editorial in the journal.

"It would take a trial with tens of thousands of patients to do that," Lange said. Nevertheless, he added, "their [the researchers'] numbers are good enough to justify its use. If you can prevent additional heart attacks, you can prevent deaths."

The second study, done in China as a joint Chinese-British effort, fills that gap, Sabatine said. It included nearly 46,000 heart attack patients treated at 1,250 hospitals. The usual practice in China is to give only aspirin to such patients, because clot-dissolving drugs are too expensive. Adding Plavix to aspirin reduced the death rate by 7 percent, said Dr. Zhengming Chen, of Oxford University in England, and a study leader.

"That large trial was designed to answer the mortality question," Sabatine said. "They do show a significant decline in mortality. This is the first time in a decade when we have a new drug for the treatment of heart attacks."

The Chinese study is especially significant for less wealthy countries, Lange said. "Plavix is not so expensive," he said. "It's not as good as giving a clot-busting medication, but more effective than giving aspirin alone."

Yet another study, this one done in Europe, showed a different benefit of Plavix. Doubling the usual dose of the drug given before angioplasty reduced the incidence of heart attacks, the need for more artery-opening procedures, and deaths, Dr. Germano Di Sciascio, professor and chairman of cardiology at Campus Biomedico University of Rome, reported at the conference on Sunday.

The trial included 255 people who underwent angioplasty. Only 4 percent of those given 600 milligrams of Plavix, double the standard dose, had a heart attack or other cardiac problem within 30 days, compared to 12 percent of those given the usual 300 milligrams, Di Sciascio said.

Another report, presented Sunday at the conference, found that St. John's wort, a medicinal herb with clot-preventing activity, appears to amplify the action of Plavix. That could raise a patient's risk for bleeding, the researchers warn.

A trial involving six people, selected because they had below-normal responses to Plavix, found that daily doses of St. John's wort given for three weeks doubled the clot-preventing activity of Plavix, researchers at the University of Michigan Cardiovascular Center reported.

They are planning a larger study to confirm the finding, but in the meantime advise patients to be candid with their doctors about any herbals they might be taking, since potentially harmful herbal-drug interactions can occur.